Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 170907
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
307 AM MDT Wed Jul 17 2019

.SHORT TERM...(Today through Thursday)
Issued at 259 AM MDT Wed Jul 17 2019

The midlevel trough has been slow to move eastward, but is
forecasted to clip northern portions of our area later today. The
moisture has also been slow to move out and there seems to be enough
to interact with the instability aloft. As a result scattered
showers and thunderstorms still continue at this hour and there is
no obvious forcing or particular location favoring development.
The NAM has somewhat depicted this activity lasting until around
sunrise. As the trough approaches drier air will filter into the
area. This air mass should support efficient mixing into fairly
decent winds speeds thanks to the tight pressure gradient
associated with the trough. Fire danger becomes critical this
afternoon below 7000 feet with Red Flag conditions for most of far
eastern Utah and western Colorado. The area where conditions are
borderline is across southwest Colorado where wind speeds might
stay below criteria, but high enough to potentially cause issues.
The chances for afternoon convection are fairly low and confined
to the San Juan mountains, which is where the remaining moisture
will reside the longest. Tomorrow the flow becomes zonal, which
continues into Friday as the upper jet stream migrates over the
US/Canadian border. The conditions may come together again to
cause Red Flag conditions in northwest Colorado tomorrow
afternoon. In fact, the minimum RH values drop into the single
digits for a large portion of the area, but the pressure gradient
relaxes enough that wind speeds remain below criteria. High
temperatures should be similar to yesterday if not a few degrees
higher given the air mass will be drier.

.LONG TERM...(Thursday night through Tuesday)
Issued at 259 AM MDT Wed Jul 17 2019

A strong trough approaching western Canada this weekend will allow
the ridge aloft to build westward over the southern plains. By
Saturday southerly flow pushes the moisture towards the region
causing a return in showers and storms. Although the lower
atmosphere will be slower to moisten so dry thunderstorms may be
the outcome for a few days. Into next week the ridge becomes
rather amplified over the western CONUS and plenty of mositure
fills in with PWAT values reaching one inch over a large area by
early week. A front moving down the Front Range may favor
convection along and east of the divide on Sunday and Monday. By
Tuesday the high pressure center is almost directly overhead as
advertised by the GFS and ECMWF. This does place the greater
moisture axis west of the forecast area, but it seems there may
be sufficient mositure to support daily terrain-driven convection
into late week. One significant difference is the strength and
track of the system that moves onshore of western Canada. The
ECMWF is much stronger therefore the ridge aloft stays suppressed
over the Four Corners while the weaker GFS builds the ridge into
the northern Rockies. This may have implications on where the
monsoon moisture surge advects. Temperatures gradually cooler
starting this weekend with the arrival of moisture and
precipitation.

&&

.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1052 PM MDT Tue Jul 16 2019

There are a few showers around KTEX and KDRO that are expected to
linger until sunrise with little to no impact on flight conditions.
Later today VFR conditions are expected as southwest winds
increase and skies become mostly sunny.


&&

.FIRE WEATHER...
Issued at 259 AM MDT Wed Jul 17 2019

Critical fire weather conditions are expected this afternoon and
evening as as dry, breezy and very warm conditions continue
across eastern UT and western CO. Conditions may still be
borderline in far southeast UT and southwest CO where winds and
RH may be around or slightly below criteria. Isolated storms are
possible over the San Juan mountains as well. High pressure will
build over all of the western U.S. by the end of the week
continuing the hot and dry conditions. Sunday afternoon will bring
the next chance of rain, with chances increasing a bit each day
next week.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...Red Flag Warning from noon today to 8 PM MDT this evening for
     COZ200-202-203-207-290-292.

UT...Red Flag Warning from noon today to 8 PM MDT this evening for
     UTZ486-487-490-491.

&&

$$

SHORT TERM...KJS
LONG TERM...KJS
AVIATION...KJS
FIRE WEATHER...KJS


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